1. Field of the Invention
The invention relates generally to the field of wellbore deployed sensors. More specifically, the invention relates to devices for clamping sensors to the wall of a wellbore to provide acoustic and/or mechanical coupling to subsurface formations.
2. Background Art
Wellbore sensors, such as wellbore seismic receivers, are used to detect signals from within wellbores drilled through subsurface formations. Seismic signals, for example, may be naturally occurring, caused by reservoir activity, hydraulic fracturing or a seismic energy source may be deployed at the Earth's surface or in another wellbore to provide seismic energy for a wellbore seismic survey.
An important element of certain types of wellbore sensors, in particular wellbore seismic receivers, is a device to urge the sensor housing into firm contact with the wall of the wellbore. Such urging is important for wellbore seismic receivers so that seismic energy may be efficiently communicated to the wellbore receiver. One type of wellbore seismic receiver is described in U.S. Pat. No. 4,715,469 issued to Yasuda et al. The device used to perform the urging function as described in the Yasuda et al. patent, for example, is typical and includes a “back up arm” that is selectively extensible and retractable from the main body of the receiver housing. When extended, the backup arm urges the housing into contact with the wellbore wall. Other devices known in the art to perform the function of urging the receiver housing against the wall of the wellbore include arched springs and permanent magnets.
The foregoing devices for urging a wellbore sensor housing against the wall of the wellbore either require considerable time to operate, cause increased friction between the receiver and the wellbore wall or both. Friction and deployment time may substantially increase the overall amount of time needed to deploy the sensor in a wellbore, thus reducing efficiency.
There is a need for improved clamping devices for wellbore sensors.